This invention relates in general to vehicle wheels and in particular to a vehicle wheel having an annular tinnerman nut clearance groove.
Referring to the drawings, there is shown in FIG. 1 a sectional view of a typical vehicle wheel, indicated generally at 10, which is formed in accordance with the prior art. The prior art wheel 10 includes an annular wheel rim 11 formed about a wheel axis 12. The rim 11 is adapted to carry a vehicle tire (not shown). The wheel 10 further includes a circular wheel disk 13 formed across one end of the wheel rim 11. The wheel disk 13 has a plurality of radial spokes 14, one of which is shown in FIG. 1, connecting the wheel rim 11 to a wheel hub 15. The spokes 14 define a plurality of openings 16 formed through the wheel disk 13. The openings 16 allow a flow of cooling air to the vehicle brakes while reducing the weight of the wheel 10.
The wheel hub 15 has a recessed center 17. The hub center 17 includes an inboard, or mounting, surface 18, which is perpendicular to the wheel axis 12 and faces the vehicle when the wheel 10 is mounted thereon. The hub center 17 also has an outboard surface 19 which is opposite from the mounting surface 18 and faces away from the vehicle when the wheel 10 is mounted thereon.
An enlarged plan view of the hub mounting surface 18 is shown in FIG. 2. The mounting surface 18 is machined flat to assure supportive contact between the wheel 10 and the surface of an adjacent vehicle suspension component (not shown), such as an axle hub, brake drum or brake rotor.
As shown in FIGS. 2 and 3, a center pilot hole 20, which is adapted to receive the end of a vehicle hub (not shown), is formed through the center of the wheel hub 15. The hub 15 also includes a plurality of stud holes 21 formed therethrough. The stud holes 21 are spaced equally about a circle 22 which is concentric with the pilot hole 20. The stud holes 21 receive threaded wheel studs (not shown) for securing the wheel 10 to the vehicle suspension component. Optional lightener pockets 23 can be formed in the hub mounting surface 18 between the stud holes 21 to reduce the weight of the wheel 10.
The wheel hub 15 further includes a shallow cylindrical recess 25 formed in the mounting surface 18 concentric with each stud hole 21. Each recess 25 defines a cylindrical surface 26 which extends axially into the mounting surface 18. The cylindrical surface 26 forms a ring-shaped shoulder 28 with the stud hole 21. The recesses 25 provide clearance for tinnerman nuts (not shown) when the wheel 10 is mounted upon a vehicle adjacent to a brake drum. Tinnerman nuts typically are wire nuts about one mm high and 25 mm in diameter which are screwed onto the wheel studs to secure a brake drum or brake rotor to an axle hub during vehicle assembly. Accordingly, the tinnerman nuts extend outwardly from the surface of the brake drum. The recesses 25 have a diameter that is greater than the tinnerman nut diameter and a depth that is greater that the tinnerman nut height. Thus, when the wheel 10 is mounted upon the vehicle, the cylindrical recesses 25 receive the tinnerman nuts, allowing the hub mounting surface 18 to fully contact the adjacent brake drum surface.
The wheel 10 can be formed by a casting operation wherein a molten metal, such as aluminum, magnesium or titanium, an alloy of a metal, or a polymer is fed into a multi-piece wheel mold. Alternatively, the wheel 10 can be formed by a forging operation wherein a heated metal billet is pressed between a pair of dies. It is known in the art to form the cylindrical recesses 25 during the forming operation. Following forming, the hub mounting surface 18 and a portion of the inside surface 11A of the wheel rim 11 are finished by a machining operation, such as turning the wheel 10 upon a lathe. The pilot hole 20 and the stud holes 21 are then drilled through the hub 15 from the outboard surface 19 with each stud hole 21 centered upon a corresponding recess 25.
Alternatively, the wheel 10 can be formed without the cylindrical recesses 25. When this is done, the hub mounting surface 18 and the rim surface portion 11A are finished as before. The pilot hole 20 and the stud holes 21 are drilled through the hub 15. Then the wheel 10 is turned over and the cylindrical recesses 25 are counterbored into the inboard end of each of the stud holes 21. It is also known to form a stud hole 21 and cylindrical recess 25 with a single combined drilling and milling operation. However, this combined operation requires a special drilling machine and tooling and is time consuming.
Vehicle wheels can also be fabricated by assembling individual components. A fabricated wheel typically includes a wheel disk that is formed from a metal, such as steel or aluminum, by a stamping, casting or forging operation. Openings in a stamped wheel disk, including stud holes, are punched through the wheel disk and concentric rings are formed around the stud holes to allow clearance of tinnerman nuts. Openings and recesses in a cast or forged wheel disk are formed as described above for a cast or forged wheel. A wheel rim is typically rolled from metal strip stock into an annular shape. Alternatively, the wheel rim can be forged or stamped. The wheel disk is attached to the wheel rim to produce a fabricated wheel.